Mode of fluid tight assembly for moderator blocks of atomic reactors



Dec. 5, 1961 G. LEMESLE ETAL MODE 0F FLUID TIGHT ASSEMBLY FOR MODERATOR BLOCKS 0F ATOMIC REACTORS 4 Sheets-Sheet 1 .lllllllll Fig.1

Dec. 5, 1961 Filed March 11, 1959 G. LEMESLE ETAL MODE OF FLUID TIGHT ASSEMBLY FOR MODERATOR BLOCKS 0F ATOMIC REACTORS 4 Sheets-Sheet 2 Dec. 5, 1961 G. LEMESLE EI'AL 3,011,961

MODE OF FLUID TIGHT ASSEMBLY FOR MODERATOR BLOCKS 0F ATOMIC REACTORS Filed March 11, 1959 4 Sheets-Sheet s 26 I za I 1 35 I Dec. 5, 1961 G. LEMESLE ETAL MODE OF FLUID TIGHT ASSEMBLY FOR MODERATOR BLOCKS 0F ATOMIC REACTORS 4 Sheets-Sheet 4 Filed March 11, 1959 11 Patented Dec. 5, .1961

3,011,961 MODE 0F FLUID TIGHT ASSEMBLY FOR MUD- ERATOR BLOCKS 0F ATOMIC REACTORS Georges Lernesie, Paris, and Pierre Rouge, Git-sur- Yvette, France, assignors to Commissariat a IEnergie Atomique Filed Mar. 11, 1959, Ser. No. 7 98,619 Claims priority, application France Mar. 15, 1958 ZClairns. ((31.204-1932) It is known that atomic reactors of the solid moderator type, such as graphite, consist of a piling up of blocks of this moderator that are made up of bars and/or prismatic pavings. The bulk of this pile is traversed by channels in which is contained the fissionable material and circulates the cooling fluid.

Cooling fluid leaks can occur at the level of the junctions between bars and/ or pavings of moderator. In fact, it is necessary on the one hand, in view of the deformations attributable to the Wigner effect brought about by the irradiations, to leave substantial clearances, and on the other hand, in view of the same deformations, the bars can become slightly tilted and the terminal surfaces of the blocks disjointed, Whichproduces gaps between them at their bases.

The leaks of cooling fluid that bring into contact neighbouring cells, i.e. groups of cartridges of fissionable material placed in adjacent channels, are very undesirable because they break the regularity of the debits-which must remain proportional to the potentials'developed in each of the cells. Nevertheless, the leaks attributable to the gaps at the base of the bars generally remain acceptable because they are relatively weak.

The present invention proposes a new mode of leakproof assembly for the moderator blocks of a solid moderator atomic reactor, which does away with all leaks of the cooling fluid at the level of the assembly components of the various blocks of the moderator,.by retaining for these components a mortise joint type of disposition.

This new mode of assembly is essentially characterized in that, between the blocks of the solid moderator to be assembled, are inserted a part of the same moderator material which has a boring coaxial with that through the channel running through the two blocks to be assembled, and oifering two plane surfaces machined perpendicularly to its direction of least Wigner effect, this part playing with respect to the assembly components of the two blocks, and that, according to a cylindrical surface, a male or female role according to the relative orientation of the main Wigner effect of the blocks to be assembled.

The intermediate part according to this invention and hereinafter referred to as rings" therefore offer either as rings having an external section sensibly equal to the internal section of a housing at the centre of the assembly components of the two blocks, and having'boring of the same axis and diameter as the channel of the pile of which it insures the imperviousness, as a parallelepiped of low height, section identical to that of the bars or paving of the pile and perforatedby a hole of the same diameter as that of the external projection of the blocks having the components of mechanical assembly.

The imperviousness is always ensured by the bearing of the plane faces of the ring, normal to the direction of least Wigner effect (generally mistaken with the direction of extrusion of the original bar) against the corresponding faces of the contiguous blocks.

The new mode of assembly, object of the present invention, offers as an advantage the suppression of leaks resulting from the interplay of the assembly components of the blocks, and a decrease, as compared to other solutions that have been offered, in the amount of wasted raw material such as spills and cuttings during fabrication.

, inal bar offers an axis of minimum expansion 5 which is' Referring more particularly to the FIGURES 1 to 5v of the attached drawings, various forms of embodiment of the invention will be hereinafter described, but it should FIGURE 2 is a schematic view of an original bar from l which is fabricated the ring, Wigner effect.

FIGURE 3 is a sketch of the centering of the assembly of FIGURE 1 before and after irradiation in an atomic pile. For the purpose of FIGURE 3 the deformations resulting from the, Wigner effect have been highly exaggerated to render the sketch easier to interpret, but in actual practice these deformations arefound not to exceed 3 or4%.

FIGURE 4 is a schematic exploded view of an assembly between a bar and a paving, according to the present invention.

FIGURE 5 is a schematic sectional view parallel to the axis of a complete assembly according to the present invention.

As seen in FIGURE '1, a pile of solid moderator, of known type, has parallelepiped shaped pavings such as 1 and 2 traversed by a cylindrical channel 3 or 4inside which are to be found the elements of fissionable material (not shown) and circulates the cooling fluid of the react or.

showing the axes of the The pavings 1 and 2 are cut from a bar of the moderator material, such as for instance graphite, obtained by ex-' trustion and offering some advantageous directions of Wigner expansion, i.e. expansion under the influence of radiations. As can be observed in FIGURE 2, the origaxes of minimum Wigner expansion being horizontal and perpendicular to each other. Mach paving has a cylindrical centering projection 8 or 9 on which are machined the tenons 10 and 11 and, perpendicularly to these the mortises 12 and 13 which are parallel to their respective axes of least Wigner expansion.

' According to the invention, a tightness ring '14 is inserted between the pavings 1 and 2. This ring is fabricated from a parallelepiped of graphite having a section identical to that of the pavings and having a hole 15 of diameter equal to that of the projections 8 and 9. The ring 14 is also manufactured so that its contact surfaces 16 and 17 are perpendicular to the direction of extrusion, therefore to the axis of least Wigner effect.

The thickness of the ring 14 is calculated by taking into account the stresses to be transmitted; account also has to be taken of the fact that a part of these stresses is transmitted directly by the tenons and mortises 3 and 9 of the pavings 1 and 2.

Under the influence of radiation, the various com-' ponents of the assembly, which is the object of the invention, are deformed, but the centering of the whole is preserved at all times: in fact, as can be seen from FIG- URE 3, the hole 15 of the ring 14- adopts a circular profile 15' since it expands isotropically, whereas the two centering projections 8 and 9 respectively adopt elliptical 3 profiles 8" and 9' since their axes of least Wigner expansion are perpendicular.

It is therefore understood from a study of FIGURE 3 that the central channel left open by the various configurations encloses a circular cylinder of constant diameter equal to that of the original channel 3 or 4 (FlG- URE 1), and that the centering of the whole is preserved by virtue of the perpendicular ovalizations.

Finally, according to the invention, the tightness of the assembly is forever preserved by the contact between the faces 16 and 17 (FIGURE 1) of the ring 14, and and 19 of each paving.

In another embodiment, described in reference to FIG- URE 4, it is. seen that a pile of solid moderator for an atomic reactor can also include, as is already known, assemblies of a paving 2t) and a prismatic rod 21.

These two blockshave coaxial channels of equal diameters 22 and 23 into which are to be found the cartridges of fissionable material (not shown). The paving 20 is machined so that its direction of least Wigner effect is parallel to two of its lateral faces 24 and 25, and perpendicular to the axis of its channel 22. The rod 21 is machined so as to have its axis parallel tothe direction of the extrusion and therefore to the axis of least Wigner effect.

The two blocks have tenons 26 and 27 and perpendicular mortises 28 and 29 which are parallel to the respective sides. The elements of the assembly extend from the outer faces of each block to a central joggle 30 and 31. The two joggles do not have quite the same diameter; that of joggle 3G, machined on the paving 2t) and being susceptible to ovalization under the influence of the radiations, is slightly larger than that of joggle 31, which is machined in rod 21 and remains perfectly circular at all times.

According to the invention, a tightness ring 32 is inserted in the assembly within the two joggles 3t and 31, the said ring being of graphite and having an internal diameter equal to that of channel 22 or 23 and an external diameter equal to that of the joggle 31 machined in rod 21. The ring 32 is machined so its axis is parallel to that of the extrusion, therefore to the axis of least Wigner etfect.

The centering of the assembly is ensured permanently by the tenons and mortises, the tightness on the other hand is ensured by the contact between the plane faces 33 and 34 of the ring 32 and the bottoms 35 and 36 of the joggles 30 and 31 respectively.

The ring 32 is always tight in the joggle 31 of rod 21 because both have parallel directions of extrusion and therefore expand similarly. On the contrary, the ring 32 is mounted with a play inside of the joggle 30; of paving 20 which can ovalize around it.

The FIGURE shows schematically a complete assembly of four blocks of solid moderator according to a preferred embodiment of the invention. The layout corresponds exactly to the superposition of those described in connection with FIGURES 1 and 4; there can be observed, from bottom to top, a bar of graphite 37, two pavings 38 and 39' and a bar 40.

The blocks are assembled according to the invention by means of rings of the male type 41 and 42 and of the female type 43. The two main axes of Wigner effect for each part being in the plane of the figure, are again indicated by their conversional signs, the third axis (not shown) easily identified by deduction for each part.

All other combinations of assemblies possible for two blocks of solid moderator with a ring according to the invention could just as well be used without departing from the scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. in atomic reactors of the type utilizing a solid moderator consisting of a pile of bloclgs shaped as bars and pavings, means for forming atight assembly between the blocks of the moderator comprising an element of moderator material inserted between two blocks to. be assembled having a passage coaxial to that of the channel extending through the two blocks, said element having two plane surfaces perpendicular to its dimension of least Wigner efifect, said element having some play with respect to the components of mechanical assembly of the two blocks, said blocks to be assembled being parallelopipeds placed one above the other with their respective axes of least Wigner expansion substantially parallel to a horizontal edge and perpendicular to each other, cylindrical projections for the blocks including tenons and mortises, said mortises being substantially perpendicular to said tenons and substantially parallel to the axes of least Wigner expansion, said element being a parallelopiped of section identical to those of the blocks, the passage in said element having the diameter of said projections and having its contacting surfaces substantially perpendicular to the axis of least Wigner effect.

2. In atomic reactors of the type utilizing a solid moderator consisting of a pile of blocks shaped as bars and pavings, means for forming a tight assembly between the blocks of the moderator comprising an element of moderator materialinserted between two blocks to be assembled having a passage coaxial to that of the chan ncl extending through the two blocks, said element having two plane surfaces perpendicular to its dimension of least Wigner effect, said element having some play with respect to the components of mechanicalassembly of the two blocks, the two blocks being parallelopipeds and being assembled vertically one above the other, one of the blocks having its direction of least Wigner eifect substantially parallel to its vertical edges, the other block having its direction of least Wignerefiect substantially parallel to a horizontal edge, mortises and tenons in the adjacent faces of the blocks at right angles to each other and with the mortise in the lower block substantially parallel to the axis of least Wigner expansion and a central joggle in the adjacent faces of the blocks, said element being a ring of external diameter equal to that of the joggle mounted in the joggle and having its axis of least Wigner effect substantially parallel to its axis.

References Cited in the file of this patent UNITED STATES PATENTS 2,852,457 Long et a1 Sept. 16, 1958 

1. IN ATOMIC REACTORS OF THE TYPE UTILIZING A SOLID MODERATOR CONSISTING OF A PILE OF BLOCKS SHAPED AS BARS AND PAVINGS, MEANS FOR FORMING A TIGHT ASSEMBLY BETWEEN THE BLOCKS OF THE MODERATOR COMPRISING AN ELEMENT OF MODERATOR MATERIAL INSERTED BETWEEN TWO BLOCKS TO BE ASSEMBLED HAVING A PASSAGE COAXIAL TO THAT OF THE CHANNEL EXTENDING THROUGH THE TWO BLOCKS, SAID ELEMENT HAVING TWO PLANE SURFACES PERPENDICULAR TO ITS DIMENSION OF LEAST WIGNER EFFECT, SAID ELEMENT HAVING SOME PLAY WITH RESPECT TO THE COMPONENTS OF MECHANICAL ASSEMBLY OF THE TWO BLOCKS, SAID BLOCKS TO BE ASSEMBLED BEING PARALLELOPIPEDS PLACED ONE ABOVE THE OTHER WITH THEIR RESPECTIVE AXES OF LEAST WIGNER EXPANSION SUBSTANTIALLY PARALLEL TO A HORIZONTAL EDGE AND PERPENDICULAR TO EACH OTHER CYLINDRICAL PROJECTIONS FOR THE BLOCKS INCLUDING TENONS AND MORTISES, SAID MORTISES BEING SUBSTANTIALLY PERPENDICULAR TO SAID TENONS AND SUBSTANTIALLY PARALLEL TO THE AXES OF LEAST WIGNER EXOPANSION, SAID ELEMENT BEING A PARALLELOPIPED OF SECTION IDENTICAL TO THOSE OF THE BLOCKS, THE PASSAGE IN SAID ELEMENT HAVING THE DIAMETER OF SAID PROJECTIONS AND HAVING ITS CONTACTING SURFACES SUBSTANTIALLY PERPENDICULAR TO THE AXIS OF LEAST WIGNER EFFECT. 